1. Field of the Invention
The invention relates generally to the testing of electronic circuits, and more particularly to systems and methods for controlling test conditions using available logic built-in self-test (LBIST) components to affect the test conditions.
2. Related Art
Electronic devices consist of many individual components that are interconnected in such a way as to provide the functionality of the device. Each of the individual components that make up the device has an associated likelihood that the component will fail. If one of the components fails, the functions performed by component will no longer be performed, so the device fails as well.
The failure rates for electronic devices normally change over time. For a typical device, the failure rate will initially be relatively high. This high initial failure rate is due to components that are defective and therefore prone to failure. For those devices that do not have any components that are defective and therefore likely to fail in this initial interval, the failure rate will drop from the relatively high initial levels to much lower levels, and will remain at these lower levels for a relatively long period of time. At some point, the failure rates will increase again as the components began to wear out. At this point, the devices have reached the ends of their useful lives, and the failures are the result of “old age,” rather than defective components.
Many product manufacturers, in order to avoid providing customers with products that are likely to fail soon after they are purchased, perform some type of testing to identify these defective products so that they will not be sold to customers. Typically, a type of testing called “burn-in” testing is used to identify these defective products. Burn-in testing simulates actual use of the product and causes the initial part of a product's lifetime to be used up in testing. This causes defective products to fail at the manufacturer's facility during testing, rather than in a customer's possession during normal operation by the customer.
After the initial portion of the product lifetime has passed and the likelihood of failure has fallen from the initial high levels to lower, acceptable levels, the product can be sold to a customer with a high level of confidence that the product will not fail for a relatively long period of time.
Burn-in testing typically simulates worst-case conditions that might be experienced by the product in normal use. For example, in the case of electronic devices, burn-in testing often entails operation of the device at high voltages, and at high temperatures. Even though the test conditions may be harsh, it is nevertheless desirable to control the test conditions so that they are applied consistently to each of the devices that undergo burn-in testing. The control of the test conditions as desirable because, while it is useful to subject the devices to the harshest conditions that may be encountered during normal use, it is counterproductive to make the conditions more harsh than could be expected, as this could cause the failure of products that would not have failed during normal use.
In order to maintain the proper conditions for burn-in testing, it may be necessary to design or purchase complicated test equipment. For instance, in the case of electronic devices such as microprocessors or other large-scale integrated circuits, it is not unusual to test the devices using expensive test machines that are capable of individually controlling the test conditions for many different devices at the same time. These test machines typically individually control the voltages provided to each of the devices, and even individually heat and/or cool the different devices to maintain the proper temperature. It is easy to understand that, because of their complexity, these test machines are typically very expensive to purchase and very expensive to operate.
It would therefore be desirable to provide systems and methods for performing burn-in testing of devices such as microprocessors or large-scale integrated circuits that eliminates the need for the complex test machinery that is currently used and it makes the burn-in testing process more efficient and more inexpensive than conventional systems and methods.